A backlight unit of the above type is disclosed by WO99/25001. The prior art backlight unit comprises a single lamp, which is bent to follow a serpentine path. There are three electrodes provided external to the lamp: one outer electrode at each extremity of the lamp and one center electrode in the middle between the outer electrodes. A supply source generates a high frequency supply voltage which is supplied to a primary winding of a transformer. The transformer has two secondary windings with two outer terminals and one common center terminal. Each secondary winding is connected to a different pair of an outer electrode and the center electrode, such, that the electrodes at the extremities of the lamp have opposite phases. Accordingly, the supply source provides lamp drivers for driving different pairs of electrodes in one manner. A goal thereof is to provide a uniform brightness distribution of light emitted by the lamp.